Developments in deep brain stimulation using time dependent magnetic fields

Abstract

The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications. KeywordsAmes Laboratory, Coils, Electric fields, Brain, Magnetic field measurements, Magnetic fields Disciplines Electromagnetics and Photonics CommentsThe following article appeared in Journal of Applied Physics 111 (2012): 07B325 and may be found at http://dx.doi.org/10.1063/1.3676623. The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models

“…This is higher than the maximum calculated magnetic field produced by the larger TMS coils typically used for stimulation of the human brain at this distance. 8 Axial magnetic field measurements were taken along the x-axis of the Magstim 25 mm double coil, at distances of 10 and 20 mm and along the coil surface using a gaussmeter and Hall probe. The measurements are shown together with calculations of the axial magnetic field in Fig.…”

“…7,8 A high-resolution anatomically realistic adult mouse model has been obtained for this study. The model is derived from MRI data of a male OF1 type mouse, of length 95 mm (excluding tail), weighing 35.5 g. 9 The model has been segmented into 50 separate and distinct tissues for which electrical properties can be independently incorporated.…”

Methods of high current magnetic field generator for transcranial magnetic stimulation application

“…Recent works have reported an enhancement on the focality and efficiency of magnetic stimulation in correlation with the depth of penetration, geometry of the coil, and the magnetic pulse duration. 3,4 There is still an ambiguity regarding the optimal design for maximum efficiency. The energy delivered to a coil for a given electric field strength is written as W ¼ …”

Focused and deep brain magnetic stimulation using new coil design in mice

“…al. [6,9] on homogeneous verses heterogeneous head modeling shows a dramatic difference in coil performance.…”

“…TMS coils that are currently used by other research groups for stimulation of animal brains are scaled down versions of standard TMS coils that are used for stimulation of the human brain [5]. Due to the variation in the physiology of the human and mouse brains, the existing Halo coil configuration was redesigned to obtain electric field values of 150 V/m which is similar to the electric field produced in an MRI derived heterogeneous human head model when stimulated using Halo coil [6]. Focality of stimulation was quantified and optimized using ratio of half value volume to the half value depth of penetration of electric field similar to the work carried out by Deng et.…”